Side branch stent graft construction

ABSTRACT

A stent graft ( 10 ) has a tubular body ( 12 ) of a biocompatible material and at least one fenestration ( 18, 20 ). The or each fenestration has a tubular side branch stitched into it with a portion of the tubular side branch extending within the tubular body and a portion of the tubular side branch extending exteriorly of the tubular body. The stitching by which the tubular side branch is mounted into the fenestration extends circumferentially and diagonally from one end of the tubular side branch to the other such that the tubular side branch extends from the tubular body at an angle thereto. The tubular side branch has a resilient ring around at least one and preferably both ends thereof and a self expanding stent in between them. The tubular side branch can have a circumferential linear portion ( 46 ) at an inner end to engage against the inner wall ( 58 ) of the tubular body. The tubular side branch can have a stent made from a single wire forming a first ring ( 45 ), a second ring ( 47 ), the second ring defining a plane which is substantially parallel to and spaced axially apart from the plane of the first ring and a number of helical wire portions ( 49 ) extending between the first and second ring. Preferably the wire is a shape memory wire such as Nitinol™wire.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority of provisional application Ser. No.60/776,423, filed Feb. 23, 2006 and provisional application Ser. No.60/773,240 filed Feb. 13, 2006.

TECHNICAL FIELD

This invention relates to a medical device and more particularly to astent graft for endovascular deployment

BACKGROUND OF THE INVENTION

Stent grafts have been devised for endovascular deployment to bypass adiseased portion of a vessel and such stent grafts can be deployed intobody vessels such as the aorta. Where there are branches from the bodyvessel such as the coeliac artery, the superior mesenteric artery andthe renal arteries it is desirable to have a fenestration in the stentgraft so that an extension arm can be placed through the fenestration toallow flow into the branch vessel.

In the renal and suprarenal region of aorta, the use of stent graft withfenestrations in the wall of the stent graft provides difficulty forcatheterisation and sealing and there have been proposed stent graftswith internal branches into which can be deployed a side arm extensionto extend from the internal branch of the stent graft into a branchvessel and so that the side arm extension can seal with in the internalbranch.

In some regions of the aorta such as the thoracic arch and the infrarenal region there is often insufficient length of stent graftproximally of the fenestration to allow an internal arm of sufficientlength to be used. If the internal arm is made too short then there isinsufficient length for sealing of the extension arm.

It is the object of this invention to provide a solution to this problemor at least to provide the practitioner with an alternative stent graftconstruction.

The invention will be particularly discussed in relation to deploymentof a stent graft into the renal and suprarenal regions of the aorta fordeployment of a stent graft into coeliac artery, the superior mesentericartery and the renal arteries, however, the invention is not so limitedand may be applied to other regions where there are branches from a maingraft such as in the thoracic arch.

Throughout this specification the term distal, when used with respect toa portion of the aorta, a deployment device or a prosthesis, means theend of the aorta, deployment device or prosthesis further away in thedirection of blood flow away from the heart and the term proximal meansthe portion of the aorta, deployment device or end of the prosthesisnearer to the heart. When applied to other vessels similar terms such ascaudal and cranial should be understood.

SUMMARY OF THE INVENTION

In one form, therefore, the invention is said to reside in a stent graftcomprising a tubular body of a biocompatible material, at least onefenestration in the tubular body and a tubular side branch sealinglyreceived in the at least one fenestration such a that an inner portionof the tubular side branch extends within the tubular body and an outerportion of the tubular side branch extends exteriorly of the tubularbody.

It will be seen that by having the tubular side branch mounted into thefenestration and extending in both directions from the fenestrationsufficient length for sealing of an extension arm into the tubular sidebranch is provided without having the tubular side branch extending toofar into the stent graft tubular body.

In the case where the stent graft according to the present invention isintended for use in the suprarenal region, the internal portion of thetubular side branch extends toward the proximal end of the stent graftfrom the fenestration.

In a preferred embodiment the tubular body has a tapered portion and thefenestration is in the tapered portion. In the region of the coeliac andsuperior mesenteric arteries, the aorta tapers as these major branchvessels extend from the aorta and tapering of the stent graft assistswith maintaining a good blood flow and pressure in the stent graft.

Preferably the tubular side branch is mounted into the fenestration bybeing stitched to the tubular body around the periphery of thefenestration.

Preferably the stitching by which the tubular side branch is mounted andsealed into the fenestration extends circumferentially and diagonallyfrom one end of the tubular side branch to the other such that thetubular side branch extends from the tubular body at an angle thereto.The fenestration may be in the tapered portion of the tubular body andwherein the stitching by which the tubular side branch is mounted intothe fenestration extends circumferentially and diagonally from one endof the tubular side branch to the other the angle between the tubularside branch and the wall of the tubular body in that region may be suchthat the tubular side branch extends substantially parallel to thetubular body as a whole.

In a preferred embodiment the tubular side branch comprises a resilientring around at least one and preferably both ends thereof. The resilientring is flexible so that it can be collapsed along with a stent graftwhen it is compressed and retailed in a deployment device but whenreleased opens to a substantially circular form and provides arelatively rigid structure against which a self expanding or balloonexpandable stent can be expanded when placing a extension arm into thetubular side branch. The resilient ring or rings my have a diameterwhich is 10% to 15% less than that of the tubular side branch. Forinstance when the tubular side branch has a diameter of 8 mm theresilient ring may have a diameter of 7 mm.

The or each ring may be formed from at least two turns and preferablythree turns of a shape memory wire such as Nitinol™wire and the ends ofthe Nitinol™wire may terminate in loops. The use of the loops preventsharp ends from the Nitinol™wire from digging into the vasculature intowhich the stent graft is deployed. The rings are stitched to the tube bystitching. The rings can alternatively be formed from stainless steelwire, plastics material or other suitable material. Stitching of theloops on the rings to the biocompatible graft material also prevents theresilient rings from being expanded by the pressure of a self expandingor balloon expandable stent placed therein and expanded.

Between the rings on the tubular side branch there may be a stent formedfrom a resilient material. The resilient stent may be formed fromNitinol™wire or stainless steel. The stent can comprise at least onehelical strut, a longitudinal strut or a zig-zag stent.

In one embodiment the resilient stent defines a cylindrical form havinga diameter less than that of the tubular side branch to define a selfcontracting stent and hence when sewn onto the outside of the tube usingstitching it provides a diameter reducing effect on the tubular sidebranch.

Also provided on the tubular side branch may be radiopaque markersadjacent each of the ends of the tubular side branch. These markersenable the physician to visualise the tubular side branch during anoperation to assist with correct placement of a leg extension into thetubular side branch.

In a preferred embodiment the tubular side branch may extend beyond thefenestration externally of the tubular body. Such an extension may haveone or more stents thereon to maintain patency.

In an alternative form, the invention is said to reside in a stent graftcomprising a tubular body of a biocompatible material, at least onefenestration in the tubular body and a tubular side branch sealinglyreceived in the fenestration such that a portion of the tubular sidebranch extends within the tubular body and a portion of the tubular sidebranch extends exteriorly of the tubular body, the portion of thetubular side branch extending within the tubular body comprising acircumferential end having a substantially linear portion and the linearportion being engaged against an inner wall of the tubular body.

It will be seen that by having the tubular side branch mounted into thefenestration and extending in both directions from the fenestrationsufficient length for sealing of an extension arm into the tubular sidebranch is provided without having the tubular side branch extending toofar into the stent graft tubular body. The linear portion of the innercircumferential end engaging against the wall provides a low profile forthe inner end within the tubular body. This also assists with enabling aphysician to extend a guide wire into the side arm because a guide wirebeing directed down along the inner wall of the tubular body will moreeasily enter the side branch where the circumference extends around andalong the wall for some distance.

In a preferred embodiment the resilient rings and the stent formedbetween the rings may be a single portion of material. Such a combinedstent and rings may comprise a portion of wire forming a first ring, asecond ring, the second ring defining a plane which is substantiallyparallel to and spaced axially apart from the plane of the first ringand a plurality of helical wire portions extending between the first andsecond ring. Preferably the wire is a shape memory wire such asNitinol™wire.

Preferably the helical portions extend in both clockwise andanticlockwise directions between the rings at each end.

Preferably each ring is be formed from but not limited to two turns of ashape memory wire such as Nitinol™wire and the ends of the Nitinol™wiremay terminate in loops. Part of each ring at each end can be formed bycircumferential portions extending from each helical portion.

In an alternative form the invention comprises a stent graft comprisinga tubular body of a biocompatible material, at least one fenestration inthe tubular body and a tubular side branch sealingly received in thefenestration such a that an inner portion of the tubular side branchextends within the tubular body and an outer portion of the tubular sidebranch extends exteriorly of the tubular body, the tubular side branchcomprises a reinforcement stent and wherein the reinforcement stentcomprises a portion of wire forming a first ring, a second ring, thesecond ring defining a plane which is substantially parallel to andspaced axially apart from the plane of the first ring and a plurality ofhelical wire portions extending between the first and second ring andwherein the inner portion comprises a circumferential end having asubstantially linear portion and the linear portion being engagedagainst an inner wall of the tubular body.

BRIEF DESCRIPTION OF THE DRAWING

This then generally describes the invention but to assist withunderstanding reference will now be made to the accompanying drawingswhich show preferred embodiments of the invention.

In the drawings:

FIG. 1 shows a first embodiment of stent graft according to the presentinvention;

FIG. 2 shows a cross-sectional view of the stent graft of FIG. 1 alongthe fines 2-2′ of FIG. 1;

FIG. 3 shows a detailed view of a tubular side branch suitable for usewith the present invention;

FIG. 4 shows a cross-sectional view of the tubular side branch of FIG.3;

FIG. 5 shows a further embodiment of the stent graft according to thepresent invention;

FIG. 6 shows a cross-sectional view of the stent graft of FIG. 5 alongthe lines 6-6′ of FIG. 5;

FIG. 7 shows an alternative embodiment of stent graft according to thepresent invention;

FIG. 8 shows a detailed view of a tubular side branch suitable for usewith the embodiment of stent graft shown in FIG. 7 according to presentinvention;

FIG. 9 shows a cross-sectional view of the tubular side branch of FIG. 8along the lines 9-9′ of FIG. 8;

FIGS. 10A, 10B and 10C show views of the combined ring and helicalportion stent used on the side arm according to one embodiment of thepresent invention;

FIG. 11 shows a view into the stent graft shown in FIG. 7 in thedirection shown by the arrow 7 in FIG. 7;

FIGS. 12A, 12B and 12C show views of combined rings and longitudinalstrut stent used on the side arm according to one embodiment of thepresent invention;

FIG. 13 shows a detailed view of a tubular side branch using the stentshown in FIG. 12; and

FIG. 14 shows a portion of a stent graft utilising the tubular sidebranch shown in FIG. 13.

DETAILED DESCRIPTION

Looking more closely at the drawings and in particular FIGS. 1 to 2showing a first embodiment of a stent graft according to the presentinvention, it will be seen that stent graft 10 has a tubular body 12which includes a tapered central region 14 and a lower parallel sidedportion 15. The tubular body is supported by stents 16. Preferably thesestents are self expanding Gianturco zig zag Z stents but other forms ofstents may also be included.

In the tapered region 14, there is a fenestration 18 and in the lowerparallel sided portion 15 of the tubular body 12 there is anotherfenestration 20. Mounted into each of the fenestrations 18 and 20 aretubular side branches 22 and 24 respectively.

As can be particularly seen in FIG. 2, the tubular side branches 22 and24 each have an inner portion 27 which extends within the tubular bodyof the stent graft and an outer portion 29 which extends outside of thetubular body of the stent graft. The tubular side branches are depictedas being longitudinally aligned with each other but theircircumferential and longitudinal position may vary depending upon theconfiguration of side arteries in the vessel into which the stent graftis to be deployed. It will be noted that in this embodiment both thetubular side branch 22 and the tubular side branch 24 have theirexternal portions facing distally.

Each of the tubular side branches 22 and 24 are stitched into theperiphery of the fenestration by stitching 30 and 30 a respectively. Thestitching extends circumferentially and diagonally from one end of thetubular side branch to the other. Where the tubular side branch 22 ismounted into the tapered portion 14 of the tubular body 12, the angledstitching 30 in fact means that the tubular side branch 22 extendssubstantially parallel to the tubular body 12.

On the other hand the tubular side branch 24 mounted into thefenestration 20 with diagonal stitching 30 a is in a substantiallystraight sided portion of the tubular body 12 and therefore the tubularside branch extends out at a angle to the tubular body 20.

Detailed construction of one embodiment of each of the tubular sidebranches is shown in FIGS. 3 and 4. FIG. 3 shows a side view of atubular side branch according to one embodiment of the invention beforeit is stitched into the fenestration in a main stent graft. FIG. 4 showsa cross-section of embodiment shown in FIG. 3 along the line 4-4′ inFIG. 3.

The tubular side branch 40 comprises a tubular body 41 of abiocompatible graft material. At each end of the tubular body 41, aresilient ring 43 is stitched onto the biocompatible material. Theresilient ring is preferably formed of two and preferably three turns ofNitinol™wire, the ends of which terminate in loops 45 which are stitchedby stitching 46 to the biocompatible graft material body 41.

Between the resilient rings 43 on the tubular side branch 40 there is astent 44 formed from a resilient material. The resilient stent may beformed from Nitinol™wire or stainless steel. The stent 44 is stitchedonto the tubular body 41 with stitching 47.

Radiopaque markers 48 are provided at each end of the tubular sidebranch so that a physician can visualise the position of the tubularside branch when operating within a patient.

The dotted line 49 shows the approximate line of stitching by which thetubular side branch 40 is mounted into the fenestrations as discussed inrelation to FIGS. 1 and 2. It will be noted that the line of stitchingextends circumferentially and diagonally from one side at one end to theother side at the other end.

FIGS. 5 and 6 show an alternative embodiment of a stent graftincorporating a tubular side branch according to the present invention.

In this embodiment, the stent graft 50 has a tubular body 52 of a graftmaterial and a tubular side branch 54 stitched into a tapered portion 56of the tubular body 52. The tubular side branch 54 is received in afenestration 58 by stitching 60. In this embodiment the tubular sidebranch 54 extends exteriorly of the stent graft with a tubular extension62 terminating in a resilient ring 64. It will be noted that in thisembodiment the tubular side branch 54 has its external portion facingdistally.

FIG. 7 shows an alternative embodiment of a stent graft according to thepresent invention. FIG. 7 uses the same reference numerals as FIG. 1 forcorresponding items. The stent graft 10 has a tubular body 12 whichincludes a tapered central region 14 and a lower parallel sided portion15. The tubular body is supported by stents 16. Preferably these stentsare self expanding Gianturco zig zag Z stents but other forms of stentsmay also be included.

In the tapered region 14, there is a fenestration 18 and in the lowerparallel sided portion 15 of the tubular body 12 there is anotherfenestration 20. Mounted into each of the fenestrations 18 and 20 aretubular side branches 22 and 24 respectively.

The tubular side branches 22 and 24 each have an inner portion 27 whichextends within the tubular body of the stent graft and an outer portion29 which extends outside of the tubular body of the stent graft.

Each of the tubular side branches 22 and 24 are stitched into theperiphery of the fenestration by stitching 30 and 30 a respectively. Thestitching extends circumferentially and diagonally from one end of thetubular side branch to the other. Where the tubular side branch 22 ismounted into the tapered portion 14 of the tubular body 12, the angledstitching 30 in fact means that the tubular side branch 22 extendssubstantially parallel to the tubular body 12.

The tubular side branch 24 mounted into the fenestration 20 withdiagonal stitching 30 a is in a substantially straight sided portion ofthe tubular body 12 and therefore the tubular side branch extends out atan angle to the tubular body 20.

It will be noted that in this embodiment the tubular side branch 22 hasits external portion facing distally and the tubular side branch 24 hasits external portion facing proximally.

Detailed construction of each of the tubular side branches shown in FIG.7 is shown in FIGS. 8 and 9.

FIG. 8 shows a side view of a tubular side branch according to oneembodiment of the invention before it is stitched into the fenestrationin a main stent graft. FIG. 9 shows a cross-section of embodiment shownin FIG. 8 along the line 9-9′ in FIG. 8.

The tubular side branch 40 comprises a tubular body 41 of abiocompatible graft material. Surrounding and supporting the tubularbody 41 is a stent 43. The stent 43 comprises an integral assembly of afirst ring 45, a second ring 47, the second ring 47 defining a planewhich is substantially parallel to and spaced axially apart from theplane of the first ring 45, and helical wires 49 extending between thefirst and second rings. The stent 43 is shown in more detail in FIG.10A. The stent may be formed from Nitinol™wire or stainless steel. Thestent 43 is stitched onto the tubular body 41 with stitching 60.

The tubular body is shaped at one end by the ring 45 having a linearportion on one side, as shown in more detail in FIG. 10B, such that thetubular body curves in at 50.

Radiopaque marker 48 is provided at the outer end of the tubular sidebranch so that a physician can visualise the position of the tubularside branch on the stent graft when operating within a patient.Radiopaque markers 48 a can also be provided at the inner end of thetubular side branch so that a physician can visualise the position ofthe tubular side branch within the stent graft when catheterising itwhen operating within a patient.

The dotted line 52 shows the approximate line of stitching by which thetubular side branch 40 is mounted into the fenestrations as discussed inrelation to FIGS. 1 and 2. It will be noted that the line of stitchingextends circumferentially and diagonally from one side at one end to theother side at the other end.

FIGS. 10A, 10B and 10C show one embodiment of construction for the stent43 as shown in FIG. 8. The stent comprises Nitinol wire of a diameter of0.006 in. formed into a first ring 45 of least two turns of wire, Asecond ring 47 formed from at least two turns of wire and helical arms49 between them. In this embodiment there are three helical wires 53extending in a clockwise direction and three wires 55 extending in ananticlockwise direction to, in effect, form a loose braid. In fact theentire stent is formed from a single length of wire starting at loop 57and terminating at loop 59. The upper ring 45 has a circumferentialshape as shown in FIG. 10B. The circumference of the ring 45 includes alinear portion 46. This linear portion 46, when the stent is installedon a side arm and the side arm is fitted into a stent graft, engagesagainst the wall of the stent graft as shown in FIG. 6.

FIG. 10C shows the shape of the rings 47 at the end of the tubular sidebranch which in use is intended to be outside the stent graft in use.

FIG. 11 shows a view into the stent graft shown in FIG. 7 in thedirection shown by the arrow 11 in FIG. 7. The side arm 22 has itslinear portion 46 engaged against the inner wall 58 of the tubular body12. The side arm 24 is mounted into the lower parallel sided portion 15.

FIGS. 12A, 12B and 12C show views of combined rings and longitudinalstrut forming a stent 60 used on the side arm according to analternative embodiment of the present invention. In this embodiment thestent 60 comprises upper and lower rings 62 and 64 joined by a singlelongitudinal strut 66. The stent is formed from a single piece ofNitinol or similar wire and the wire terminates in respective loops 68and 69. FIG. 12B shows the ring 64 with loop 69 and a flattened portion65 which fits against the inner wall of the stent graft as discussedearlier. FIG. 12C shows the ring 62 with the loop 68.

FIG. 13 shows a detailed view of a tubular side branch using the stentshown in FIG. 12. The tubular side branch 70 comprises a tubular portionof biocompatible graft material 72 with the stent 60 outside of it sothat the ring 62 is at one end of the tubular body and the ring 64 is atthe other end of the tubular body and the strut 66 extends along theoutside of the tubular body. The rings 62 and 64 are stitched to thetubular body by stitching 74 and the strut 66 is stitched to the tubularbody by stitching 76.

FIG. 14 shows a portion of a stent graft utilising the tubular sidebranch shown in FIG. 13. The stent graft 80 has a fenestration 82 intowhich the tubular side branch 70 is sewn. One of the stents 84 of thestent graft 80 passes over the tubular side branch 70. Radiopaquemarkers 86 are provided on the terminal end of the tubular side branch70.

Throughout this specification various indications have been given as tothe scope of this invention but the invention is not limited to any oneof these but may reside in two or more of these combined together. Theexamples are given for illustration only and not for limitation.

Throughout this specification and the claims that follow unless thecontext requires otherwise, the words ‘comprise’ and ‘include’ andvariations such as ‘comprising’ and ‘including’ will be understood toimply the inclusion of a stated integer or group of integers but not theexclusion of any other integer or group of integers.

1. A stent graft comprising a tubular body of a biocompatible material,at least one fenestration in the tubular body and a tubular side branchsealingly received in the at least one fenestration such a that an innerportion of the tubular side branch extends within the tubular body andan outer portion of the tubular side branch extends exteriorly of thetubular body.
 2. A stent graft as in claim 1 wherein the inner portionof the tubular side branch extends toward the proximal end of the stentgraft from the fenestration.
 3. A stent graft as in claim 1 wherein thetubular body has a tapered portion and the fenestration is in thetapered portion.
 4. A stent graft as in claim 1 wherein e tubular sidebranch is mounted into the fenestration by being stitching to thetubular body around the periphery of the fenestration.
 5. A stent graftas in claim 4 wherein the stitching extends circumferentially anddiagonally from one end of the tubular side branch to the other suchthat the tubular side branch extends from the tubular body at an anglethereto.
 6. A stent graft as in claim 1 wherein the tubular side branchcomprises a resilient ring around one or both ends thereof and the oreach ring is formed from one to three turns of a shape memory wire andthe ends of the wire terminate in loops and the or each ring is formedfrom stainless steel wire, plastics material or other suitable material.7. A stent graft as in claim 1 comprising a stent formed from aresilient material on the tubular side branch.
 8. A stent graft as inclaim 7 wherein the stent is selected from a group comprising at leastone helical strut, a longitudinal strut or a zig-zag stent.
 9. A stentgraft as in claim 1 wherein the tubular side branch comprises radiopaquemarkers on the outer portion of the tubular side branch.
 10. A stentgraft as in claim 1 wherein the tubular side branch extends beyond thefenestration externally of the tubular body.
 11. A stent graft as inclaim 6 wherein the ring at the inner end of the side branch comprises alinear portion and the linear portion is engaged against an inner wallof the tubular body.
 12. A stent graft as in claim 1 wherein the tubularside branch comprises a reinforcement stent.
 13. A stent graft as inclaim 12 wherein the reinforcement stent comprises a portion of wireforming a first ring, a second ring, the second ring defining a planewhich is substantially parallel to and spaced axially apart from theplane of the first ring and a plurality of helical wire portionsextending between the first and second ring.
 14. A stent graft as inclaim 13 wherein the helical wire portions extend in both clockwise andanticlockwise directions between the rings at each end.
 15. A stentgraft comprising a tubular body of a biocompatible material, at leastone fenestration in the tubular body and a tubular side branch sealinglyreceived in the at least one fenestration such that an inner portion ofthe tubular side branch extends within the tubular body and an outerportion of the tubular side branch extends exteriorly of the tubularbody, the inner portion of the tubular side branch comprising acircumferential end having a linear portion and the linear portionengaged against an inner wall of the tubular body.
 16. A stent graftcomprising a tubular body of a biocompatible material, at least onefenestration in the tubular body and a tubular side branch sealinglyreceived in the fenestration such a that an inner portion of the tubularside branch extends within the tubular body and an outer portion of thetubular side branch extends exteriorly of the tubular body, the tubularside branch comprises a reinforcement stent and wherein thereinforcement stent comprises a portion of wire forming a first ring, asecond ring, the second ring defining a plane which is substantiallyparallel to and spaced axially apart from the plane of the first ringand a plurality of helical wire portions extending between the first andsecond ring and wherein the inner portion comprises a circumferentialend having a substantially linear portion and the linear portion beingengaged against an inner wall of the tubular body.